I am so close to being done with this infant sweater. I am just doing stockinette stitch. I made a mistake and had to rip out a couple rows. Somehow my working yarn ended up on the second to last stitch on the needle instead of the last- does that make sense? I thought maybe I ripped one stitch too many. So as I continued knitting, that edge of the garment doesn't look right. I know I have to rip out again (back to b4 my mistake) but what am I doing wrong? Ripping too far?

Sounds like it--if you're doing what sometimes happens to me. I rip out X # of rows, and sometimes the first stitch of the next row pops out, too. Just flip your knitting, knit that last stitch of the row you wanted in tact, and then turn and start on the rows you wanted ripped out. This is after you rip it out the second time, of course! Been there...

This sounds like what happens to me often, I'm a bit clumsy or unlucky or tinking and my last stitch of a completed row falls off the needle and undoes itself, and I put the (now unknitted) last stitch back on the needle, so the working wool is coming off the second-to-last stitch.

To fix it I put the full needle in my right hand and the empty needle in my left. Now I put the last stitch onto the empty left needle. I have (for example) nineteen knitted stitches on the right needle with the wool coming off that last stitch, and one unknitted stitch on the left needle, just like you do at the end of a row when you haven't knitted that one last stitch left. Knit this normally, just as you would do at the end of the row.
Sarah